Vulnerability identifier: #VU40985

Vulnerability risk: Medium

CVSSv3.1: 4.6 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2014-3556

CWE-ID: CWE-77

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
nginx
Server applications / Web servers

Vendor: NGINX

Description

The vulnerability allows a remote non-authenticated attacker to gain access to sensitive information.

The STARTTLS implementation in mail/ngx_mail_smtp_handler.c in the SMTP proxy in nginx 1.5.x and 1.6.x before 1.6.1 and 1.7.x before 1.7.4 does not properly restrict I/O buffering, which allows man-in-the-middle attackers to insert commands into encrypted SMTP sessions by sending a cleartext command that is processed after TLS is in place, related to a "plaintext command injection" attack, a similar issue to CVE-2011-0411.

Mitigation
Install update from vendor's website.

Vulnerable software versions

nginx: 1.5.0 - 1.5.12, 1.6.0 - 1.6.1, 1.7.0 - 1.7.3

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External links
http://mailman.nginx.org/pipermail/nginx-announce/2014/000144.html
http://marc.info/?l=bugtraq&m=142103967620673&w=2
http://nginx.org/download/patch.2014.starttls.txt
http://bugzilla.redhat.com/show_bug.cgi?id=1126891

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.